T RELATIONS BETWEEN STRENGTH AND POWER TESTS AND THE SHORT-DISTANCE SWIMMING SPEED AMONG YOUNG SWIMMERS

Swimming, as a sport where the goal is to be faster, to a great extent depends on the manifestation of strength and power at short distances. An evaluation of dry land strength and power is an important part of the training process, but the evaluation of dry land measurents and its influence on swimming results is problematic, considering the fact that the manifestation of strength and power in the water is specific in comparison to dry land. The aim of this paper is to determine whether there is a correlation between the results of the tests of strength and power from the Eurofit battery test and short-distance swimming speed among young swimmers. The sample of participants consisted of 27 swimmers aged 13 ± 2.1 year. The results of Pearson’s coefficient and regression analyses indicate that there is a high correlation between the tests of the standing broad jump and the sit-ups with the average swim speed at a distance of 50 (r = 0.656, r = 0.833, respectively) and 100 m (r = 0.746, r = 0.640, respectively), as well as swim time at a distance of 50 (r = -0.623, r = -0.856, respectively) and 100 m (r = 0.723, r = 0.687, respectively) freestyle. We can conclude that the standing broad jump and the sit-ups tests of the Eurofit battery tests could be predictors in conclusion about factors of swim speed at short distances among young swimmers, that is, are suitable for the selection of young swimmers.


INTRODUCTION
Strength and power play an important role in most sports, and thus in swimming as well.Swimming, as a sport where the goal is to be faster, to a great extent depends on the manifestation of strength and power (Sharp, Troup, & Costill, 1982;Garrido et al., 2010;Morouco et al., 2011).This is especially pronounced at short distances, where explosive and maximum strength and power play a decisive role (Hawley & Williams, 1991;Strzala & Tyka, 2009;Garrido et al., 2010;Morouco et al., 2011).
An evaluation of dry land strength and power in swimming is an important and constituentpart of the training process (Smith, Norris, & Hogg, 2002).Data of the manifested strength and power can give insight into whether strength and power training was effective as well as whether the training was focused on ies indicate that there is a high correlation between the characteristics of strength and power measured on dry land and swim speed at short distances, both among older (Sharp et al., 1982 The differences among the research results can be ascribed to the test validity and used measuring instruments.As we have already mentioned, swimming is a specific sport, where the manifestation of strength and powerin water significantly differs from the manifestation of dry land strength and power.Thus, not all measuring instruments are suitable for the study of the correlation between dry land strength and power and performances in water.Tests for the evaluation of strength and power in swimming should make sure that movement during task performance does not deviate from specific movement in water (Smith et al., 2002).However, the measuring instruments for this type of evaluation are expensive and are often unavailable to coaches and experts in the field of swimming.This is especially a problem when working with young swimmers.Certain authors indicate that for young swimmers no expensive or complicated or time-consuming equipment is needed to evaluate dry land strength and power (Silva et al., 2007).Also, one of the knowledge drawbacks of previous studies is that most of them were limited to analyzing the strength and power of the muscles of the arms and shoulder belt, even though the muscles of the legs, abdomen and back play an important role in swimming (Deschodt et al., 1999;Toussaint et al., 2006;Keiner et al., 2015).
Very few studies have focused on the correlation between tests of strength and power from the Eurofit battery test and swimming speed.The Eurofit battery of tests is a widely used battery of tests which are sim-ple to use, reliable for the evaluation of motor skills, and the results of these tests can be compared to the results of tests obtained for participants of the same age throughout all of Europe.What is most important is that the battery is available for use and does not require any expensive equipment, which is of great importance, especially for experts who work with children (Oja & Tuxworth, 1995; Tsigilis, Douda, & Tokmakidis, 2002; Gajević, 2009).
The subject matter of this research is the evaluation of dry land strength and power among young swimmers.The aim of the paper is to determine whether there is a correlation between the results of the tests for strength and power from the Eurofit battery and swim speed at short distances among young swimmers.Based on the obtained results it can be determined whether the tests for strength and power from the Euroft battery are suitable for the evaluation of the strength and power of young swimmers, that is, whether they can be predictors of swim speed among young swimmers.It is assumed that certain tests will indicate a high correlation with the swim speed of young swimmers.

Participants
The sample of participants consisted of 27 swimmers, 15 boys and 12 girls (Age: 13 ± 2.1, BH = 156.1 cm, BW = 47.3 kg, BMI = 18.9 kg/m²).All of the participants were active swimmers, had trained swimming for at least 3 years and actively competed in their age categories.The participants and their parents were familiar with the aim and purpose of the study and had voluntarily agreed to participate in it.All the study procedure were carried out in accordance with the Declaration of Helsinki and the rules of the Ethics Committee of the Faculty of sport and physical education University of Priština.

Sample of variables
The sample of variables consisted of 4 variables for the evaluation of swimming speed and 3 variables for the evaluation of muscle strength and power.The variables used to evaluate swim speed included (Geladas et al., 2005; Toskić, D., Lilić, & Toskić, L., 2016): be able to best express their optimal abilities in water and on dry land.The time and average swim speed were measured in a pool 50 meters in length, while strength and power were measured in additional swimming facilities.The participants swam a distance of 50 (t50; ν50) and 100 m (t100; ν100) at maximum speed, in two different days.The testing of muscle strength and power was carried out in accordance with the rules and procedures of the Eurofit battery test.The measuring of speed, that is, swim time and the measuring strength and power were carried out on different days so that the participants could be able to rest.All of the measuring were carried out by the same experienced invigilators.

Statistical data analyses
In this paper we used a descriptive statistical procedure (Mean, SD, cV%, Min, Max), Pearson's correlation coefficient and linear regression analysis.Descriptive statistics were applied in order to describe the measured variables, while the correlation coefficient and linear regression analysis were used in order to determine the correlation and character of the correlation between the measured variables.The level of statistical significance was calculated at 95 % with p < 0.05 (Hair et al., 1998), while all of the statistical procedures were performed using the SPSS 19 program (IBM).

RESULTS
Table 1 shows the descriptive indicators of swim speed and time for the 50 and 100 m front-crawl technique as well as the results of the tests of power and strength for the young swimmers.As it can be notised, the participants' average swim time for the 50 m front-crawl of 36.8 s and an average swim speed of 1.46 m/s, while the average swim time for the 100 m was 85.9 with an average swim speed of 0.56 m/s.Based on the indicators of the result homogeneity (cV %) it can be concluded that the participans were homogenous in the case of this variable.In the case of the tests results for the evaluation of strength and power it can be concluded that the average results for the SBJ was 148.7 cm, the average number of sit-ups • swim time to 50 m (t50) • average swim speed to 50 m (ν50) • swim time to 100 m (t100) • average swim speed to 100 m (ν100) Average swim speed is calculated by dividing swimming distance with time that was needed to swim that distance.Swim speed at 50 m is calculated by taking the covered distance, without the length of the jump, and dividing it by the time needed to swim it, while for the 100 m sprint the time needed for the turn was also included in the calculation.Swimming tests were recorded with camera and length of the start and turn was determined as a point of the first arm exit on the surface of the water.
The variables for the evaluation of strength and power included: • standing broad jump (SBJ) -to evaluate the explosive power of the leg muscle extensors • sit-ups (SUP) -to evaluate the muscular strength and endurance of the abdominal flexors • bent arm hang (BAH) -to evaluate the muscular endurance and functional strength of the muscles of the arms and the shoulder belt.
The tests for the evaluation of strength and power used in this study were taken from the Eurofit battery of tests (Council of Europe, 1988; Kemper & Van Mechelen, 1996; Jürimäe, Volbekiene, Jürimäe, & Tomkinson, 2007).These variables, as well as the Eurofit battery test, were chosen for their availability and simplicity.As previously mentioned, other more precise measuring instruments must be available to evaluate the aforementioned abilities.However, these instruments are often quite expensive and unavailable to swimming coaches who work with children.The selected tests do not require any expensive equipment, are simple to use, valid for the evaluation of certain abilities and the results of these measuring can be compared to the results of other participants of the same age from all of Europe.

The testing procedure
All of the measurements were taken under the same conditions.The participants were all healthy, rested and all of the tests were carried out in the morning.Prior to the testing, warm up was done so that no injuries would occur and so that they would Graphs 1 to 8 have indicated statistically significant correlations between the tests results for the evaluation of strength, power and speed, that is, swim time for the 50 and 100 m front-crawl.It can be concluded that there is a high and statistically significant correlation between the variables SBJ, average swim speed for the 50 (r = 0.656, p = 0.000) and 100 m (r = 0.746, p = 0.000) front-crawl as well as swim time for the 50 (r = -0.623,p = 0.001) and 100 m (r = -0.723,p = 0.000) front-crawl.The variable SUP has a high and statistically significant connection with swim speed for the 50 (r = 0.833, p = 0.000) and 100 m (r = 0.640, p = 0.000) front-crawl, as well as swim time for 50 (r = -0.856,p = 0.000) and 100 m (r = -0.687,p = 0.000) front-crawl.The BAH test is not correlated to the variables used to evaluate swim speed for the 50 and 100 m front-crawl in a statistically significant way.

DISCUSSION
In this study, on a sample of 27 young swimmers, it was studied the correlation between the test results for strength and power from the Eurofit battery and swim speed at short distances.Based on the obtained results it can be concluded that the tests of power and strength from the Eurofit battery are suitable for the evaluation of strength and power among young swimmers, that is, administrated tests can be predictors of swim speed among young swimmers.
Table 1 shows the descriptive indicators of time and swim speed for the 50 and 100 m front-crawl as well as the tests results for the strength and power of young swimmers.This group of participants are especially homogenous when it came to swim time and average swim speed, which is an expected result considering that we are dealing with swimmers who had 3 years of training experiance.Based on the descriptive indicators of the tests results for the strength and power it can be concluded that the greatest homogeneity of the results was obtained for the SBJ test and the lowest for the BAH test.These results were expected considering that this group of participants is involved in swimming, works on developing the strength of the leg extensors, which has great influence on one of the important parts of a race, the start (West, Owen, Cunningham, Cook, & Kilduff, 2011), and thus manifest great and homogenous results in the case of this particular ability.The pronounced lack of homogeneity in the results for the BAH test is also understandable considering that muscle strength to a great extent depends on body mass, which in this period of growth and development varies (Samson et al., 2000).In addition, isometric strength endurance of the arm muscles and the shoulder belt is an ability which plays an important role in swimming, but coaches do not ascribe a lot of importance to the development of this ability, so it can be assumed that this is one of the reasons for the exceptionally nonhomogenous results for this variable.When this results of nonexperimental investigation are compared with the results of similar studies which were carried out on similar samples, it can be, in generally, concluded that this group of participants are average in terms of swim speed and the measured characteristics of strength and power or their age group (Gajević, 2009;Garrido et  Results of this study indicate that there is a statistically significant correlation between the tests results for the evaluation of strength and power from Eurofit battery test and speed, that is, swim time for the 50 and 100 m front-crawl in young swimmers (Graph from 1 to 8).This means that participants who have achieved better results for the SBJ and SUP tests will swim the 50 and 100 front-crawl much quicker at a greater average swim speed, that is, the participants who manifest a greater level of explosive power of the extensor muscles of the legs and greater strength and endurance for the flexor muscles of the abdomen achieve better results when swimming shorter distances.These results agree with those of previous studies in the field, whose results speak in favor of the fact that there is a high correlation between dry land muscle strength and power and swimming performances ( Results obtained in this study are expected.As was previously mentioned, it was proven that efficient start is a part of achieved results, and that start is an important part of the race, that is, success in swimming, especially at short distances.Kinetic and kinematic attribute of start to a great extent depends on muscle strength and power (West et al., 2011) of the leg extensors.Swimmers who manifest greater maximum and relative power, as well as maximum, that is, relative strength over a short period of time (RFD), have a quicker and more efficient start.Thus, there is a logical correlation between swim speed at short distances and the explosive power of the leg extensors among young swimmers.It can be assumed that young swimmers who have greater explosive power of the leg extensors will have a better and more efficient start, which creates the preconditions for the greater initial and thus for calculating the average swim speed at short distances, as well as better overall swim time.
A high correlation between strength and endurance of the torso flexors and speed, that is, swim time for short distances was also expected.It was indicated that the torso flexors play an important role in the propulsive leg work (Magnusson, Constantini, McHugh, & Gleim, 1995).This is especially pronounced at short distances, where it is necessary to perform multiple leg kicks over a shorter period of time.Young swimmers who have greater strength and endurance of the torso flexors, that is, those who can do more seated torso lifts during 30 s have more intense leg kicks, that is, can swim at greater speed over a short period of time during short-distance races.
The obtained results also indicate the fact that the SBJ test has a higher correlation with swim time and average swim speed at a distance of 100 m, while the SUP has a greater correlation to the swim time and average swim speed at a distance of 50 m.The greater correlation between explosive power of the leg extensors and time, that is, swim time to 100 m can be explained by the fact that explosive power of the leg extensors at a distance of 100 m is manifested not only during the start but also the turn.The consequence of a greater correlation between the strength and endurance of the torso flexors and speed, that is, time to 50 m can be explained with more intense strokes, that is, more intense leg kicks at shorter distances.In addition, the SBJ test has a greater correlation with swim speed, while the SUP test has a greater correlation with swim time to 50 and 100 m.
It has shown that there is no statistically significant correlation between results of the BAH test and variables used to evaluate performance in water.In other words, strength and endurance of the muscles of the arms and shoulder belt is not correlated to the speed and time to 50 and 100 m among young swimmers.These are inntersting results which demand further analsys because their simplified interpretation coul lead to conclusion that isometric strength and endurance of the arm and shoulder belt muscles does not play an important role in swimming.It can be concluded that swimmers do not to a great extent participate in exercises and activities from this test.This result is similar to those found in a certain number of similar studies, and which speak in favor of the fact that there is no statistically significant correlation between certain tests for the evaluation of strength and power and swim speed (Johnson, Sharp, & Hendrick, 1993; Crowe, Babington, Tanner, & Stager, 1999; Dominguez-Castelss & Arrelano, 2011).

CONCLUSION
Based on the obtained results it can be concluded that there is a high and statistically significant correlation between chosen test from Eurofit battery and time and swim speed for the 50 and 100 m frontcrawl among young swimmers.Young swimmers who manifest a greater level of explosive power of the leg extensors and strength and endurance of the torso flexors swim the 50 and 100 m front-crawl with a greater average swim speed.It can be concluded that the above mentioned strength and power tests from Eurofit baterry are good predictors for of swim speed develoopment at shorter distances and are suitable for use during the training process of young swimmers.
Further studies in this field are necessary, studies which would include a greater sample of swimmers of different techniqies and disciplines so as to be able to confirm the predictive values of dry land measurements and its influence on swimming skills.

Graph 1 .Graph 2 .Graph 3 .Graph 4 .Graph 5 .Graph 6 .Graph 7 .Graph 8 .
Correlation between the tests results of the SBJ test and swim speed to 50 m Correlation between the test results of the SUP test and swim time to 50 m Correlation between the tests results of the SBJ test and swim speed to 100 m Correlation between the test results of the SBJ test and swim time to 100 m Correlation between the tests results for the SUP test and swim speed to 50 m Correlation between the results of the SUP test and swim time to 50 m Correlation between the results of the SUP test and swim speed to 100 m Correlation between the results of the SUP test and swim time to 100